It is generally acknowledged that no one can determine the actual day of Christ’s birth. Several candidates enjoyed popularity in various parts of the late Roman world, some in the spring. The most popular choice, though, was January 6, Epiphany. Yet the Roman church adopted December 25. Why?
A currently popular view regards Christmas as a hijacking of the Saturnalia, a somewhat pagan raucous event, which started on December 17 and extended to from three to seven days thereafter—but never, it seems, reaching as far as the 25th. In addition, some have suggested the winter solstice as a source, but that is fixed at December 22. Near misses don’t qualify, for the Romans insisted on precision in these calendrical matters. The reason for this emphasis is that astrology, then widely accepted, required determination not just of the actual day of one’s birth, but the hour. (By the way, has anyone ever calculated Jesus’s horoscope based on the several candidates for his proposed birth?)
To make a long story short, Christmas in fact coincides with an observance established by the emperor Aurelian in AD 274: December 25 was fixed as the birthday of the Unconquered Sun (Sol Invictus).
Late antiquity saw the rise of a contentious welter of religions. Of Middle Eastern origin, the Unconquered Sun came to enjoy wide appeal because of its lack of specificity. While it connoted potency, the Sol Invictus otherwise had a kind of neutrality that gave it appeal to a number of competing religious factions. It was cosmic, not anthropomorphic, at least not necessarily so. For traditional pagans Sol Invictus was identical with Apollo, originally a Greek import. The Mithraists saw it as a manifestation of their Mithras Helios. Christians could honor the solar deity as a metaphor for the "Sun of Righteousness," that is, Jesus Christ. Interestingly, the soil underneath the basilica of St. Peters has yielded a mosaic, apparently of the early 4th century, showing Christ as a sun god riding a chariot.
While the Roman Church, and eventually the entire Latin West, adopted December 25 to mark the Nativity, the eastern holiday of Epiphany was retained as well. Today the 6th of January is observed in Hispanic countries as the day of the Three Kings (the Magi), when gifts are exchanged. In this way, the old Roman observation of New Year’s Day, the first of January, was bracketed by Christmas, on the one hand, and Epiphany, on the other. They were two bookends, as it were, enclosing the older date for the beginning of the civil year. (For the Church Christmas was the beginning of the year.) The combination attests a widely ramifying process: retention of traditional holidays—providing that their pagan character was not overt--while mingling them with the new.
As part of this inquiry I looked into one of the major sources for late Roman festivals, the Calendar of 354. This richly illustrated volume, made for a cultivated Christian named Valentinus, is actually a composite reference book recording the public religious festivals in Rome (roughly the first half), together with Christian parallels (the second half). While this combination may at first sight seem schizophrenic, or at best a shotgun marriage, it actually accords well with an era of transition. Valentinus, the book’s owner, wished to have a record of the festivals of his ancestors, as well as the holy observances of his own faith. Many of the old festivals were falling into desuetude in his own day, and new deities, more acceptable to Christians and those adhering to other salvific religions, came in, favored because of their relative neutrality. These included Roma Aeterna, a personification of the city; Salus, or public safety; and the aforementioned Sol Invictus.
The original for the Calendar of 354, our best source for these matters, has been lost. Yet it has been reconstructed by several generations of classical scholars. The results of these labors have been summed up by Michele Renee Salzman in her fine monograph, On Roman Time (Berkeley, 1990).
Now for a fast forward. Somewhat analogous to the transitional picture recorded by the Calendar, we can observe changes in our own practice. Since 1954, Armistice Day, devised to commemorate the end of World War I on November 11, has been renamed Veterans Day. Washington’s and Lincoln’s birthday get rolled together as President’s Day, while a new holiday has appeared to honor Martin Luther King.
Today controversy surrounds Christmas. For some time it has had two rivals, Hanukkah and Kwanzaa. In many of the "blue" (liberal) states it is no longer fashionable to say "Merry Christmas"—one should call out "Happy Holidays" instead. In some cases Nativity scenes and Christmas carols have been banned from public observance, ostensibly on grounds of separation of church and state.
Christmas is a national holiday in the United States. Yet in its origin it is a religious holiday. In a sense we have come full circle, back to the duality of late Roman times. The day of the Unconquered Sun was a holiday in the perfected version of the official (pagan) calender. Yet Roman Christians could also accept this figure as the avatar of their own founder. Hence Christmas as we know it.
Like everything else in human culture, holidays evolve. As in 4th-century Rome, these changes can occasion controversy, with some urging radical change and others defending the status quo. Whatever the case, it seems that Christmas will be with us a good deal longer.